You have discovered an in a bacterium that is only turned on

You have discovered an in a bacterium that is only turned on when sucrose is present and glucose is absent. You have also isolated three mutants which have changes in the upstream sequences of the and whose behavior is summarized below. You that there are two gene regulatory sites in the upstream regulatory sequences, A and B, which are affected by the mutations, + indicates a normal site, and - indicates a mutant site that no longer binds its gene regulatory protein. Give that mutant 1 has sites A-B+, is the gene regulatory protein that binds to site A is A repressor An activator

Solution

4. When there is a mutation in the A site, the transcription of the operon is shut off in the presence of sucrose. This means that the gene regulatory protein binding to site A acts as a repressor, which is shutting off the transcription of the operon.

5. The regulatory protein binding to the site A also binds to sucrose. When the sucrose is present in the media, it binds to regulatory protein by which it will not be able to bind to the site A.